The present invention relates to a method for manufacturing a planar micro-lens for use in a liquid crystal display element and so on, and relates to a planar micro-lens being characterized by the lens material thereof.
A liquid crystal display element is used in a projector television (PTV). In this liquid crystal display element, wherein a liquid crystal is put into a gap defined between two (2) pieces of glass plates, a TFT (thin film transistor) is formed from amorphous silicon and/or polysilicon, upon a surface of each of site glass plates facing to the liquid crystal, corresponding to each of pixels.
And, in the PTV using a penetrative type of liquid crystal display element therein, an illumination light is irradiated from a xenon lamp or a metal halide lamp, etc., upon the liquid crystal display element, so that it penetrate through pixel openings of the liquid crystal display element to an exit side, thereby projecting a picture or video image formed on the liquid crystal display element through a projection lens onto a screen.
For brightening the above-mentioned projection picture through collecting or condensing the above-mentioned illumination light onto the pixel openings, so as to increase the ratio of the illumination light penetrating through the liquid crystal display element, a planar micro-lens is connected or bonded on one of the two (2) pieces of glass substrates constructing the liquid crystal display element, at a side upon which the illumination light is incident, so that the illumination light is condensed onto the pixel openings, and a method for manufacturing such planar micro-lens is known, as is disclosed, for example, in Japanese Laid-Open Patent Hei 7-225303 (1995). Also, further methods are known, such as those disclosed in Japanese Laid-Open Patent Hei 2-42401 (199), Japanese Laid-Open Patent Hei 2-116809 (1990), and U.S. Pat. No. 5,513,289.
Explanation of the manufacturing method of the planar micro-lens disclosed in the Japanese Laid-Open Patent Hei 7-225303 is as below, explained with reference to to FIGS. 20(a) through (h).
First, as shown in FIG. 20(a), a light sensitive film is formed on a surface of the substrate, and an electron beam is irradiated on the light sensitive film so as to form the lens portion, as shown in FIG. 20(b), thereby producing a master disc of the micro-lens array.
Next, as shown in FIG. 20(c), upon the surface of the master disc of the micro-lens array is laminated nickel or the like through an electrocast method, and further, as shown in FIG. 20(d), the laminated body is separated or removed from the master disc of the micro-lens array, thereby producing a stamper.
Then, as shown in FIG. 20(e), an ultraviolet ray curable resin is poured into recess portions of the stamper, and as shown in FIG. 20(f), it is extended while being pushed down by a transparent substrate, and further as shown in FIG. 20(g), the ultraviolet ray curable resin is cured, and thereafter as shown in FIG. 20(h), the ultraviolet ray curable resin is separated from the stamper together with the transparent substrate.
Then, upon the surface of the separated transparent substrate, on which the lens portions are formed from the ultraviolet ray curable resin, a cover glass is fitted to be bonded on it, by pouring an adhesive resin of low refraction index to be contained between the facing surfaces thereof, thereby forming the planar micro-lens.
The lens portions are formed by means of irradiating an electron beam upon a resist in the above-mentioned method, however it is difficult to form a microscopic lens by this method with high precision or accuracy.
Also, for the planar micro-lens to be installed within a liquid crystal display device, it is desirable to be of a dense type, in which a large number of the lens portions are aligned closely without gaps between them in the plane view thereof, however it is difficult to produce such the dense micro-lens array through such a conventional manufacturing method as that mentioned above.
Further, for manufacturing the liquid crystal display device, it is also necessary to form elements or components such as transparent electrodes, an orientation film, a black matrix, etc., on a surface of the above-mentioned cover glass facing to the liquid crystal. Since the steps for the forming of those elements must be conducted under heating, it is therefore determined that resin materials forming the lens and the adhesive layers should not be such ones that may be subject to thermal cracking and/or thermal deformation and decreases of transparency thereof, and in the Japanese Laid-Open Patent Hei 7-225303 (1995) are listed various materials being commercially available for use as resins heat-resistant against temperatures of 150xc2x0 C. or more. However, in actual practice, by taking the temperature for forming the transparent electrodes and the orientation film with a spattering method, etc., into consideration, heat-resistance against 150xc2x0 C. or more is not great enough resistance, since there can be easily caused a change of color (i.e., transparent material changed in color to yellow), separation, cracks, dimness, etc., therefore at least a heat-resistance to temperatures of 180xc2x0 C. or more is required for the resin material having high refraction index, which is used as the lens portion in particular.
In accordance with the present invention, for dissolving such problems of the conventional arts as those mentioned above, a first object is to provide a method for manufacturing a planar micro-lens, with which microscopic lens portions can be formed on the surface of a glass substrate with high precision or accuracy, and a second object is to provide a planar micro-lens having a superior hear-resistance thereof.
For achieving the first object, according to the present invention, there are provided methods relating to the present claims 1 through 3, assuming that each of them is based upon a method for manufacturing a planar micro-lens, having a high refractive index resin material and a low refractive index resin material, being laminated in layers within a region defined between a first glass substrate and a second glass substrate, wherein microscopic spherical surfaces or microscopic cylindrical surfaces are aligned on a boundary surface of the two kinds of the resin materials in a single dimension or two dimensions, wherein the method for manufacturing a planar micro-lens defined in claim 1 comprises the following first through sixth steps:
(First step)
a step for forming a large number of microscopic recess portions forming cylindrical or spherical surfaces on a surface of a glass substrate in a single dimension or two dimensions, by conducting a wet etching through a mask upon the surface of the glass substrate as a forming die;
(Second step)
a step for aligning the large number of the microscopic recess portions densely, by again conducting the wet etching upon the surface of the glass substrate as the forming die on which the microscopic recess portions are formed in the first step, but not through the mask;
(Third step)
a step for applying a separating agent upon the surface of the glass substrate as the forming die having the microscopic recess portions aligned densely being formed in the second step, and further for applying a light-curable or heat-curable resin material of high refractive index thereon;
(Fourth step)
a step for curing the high refractive index resin material, after piling a first glass substrate upon the high refractive index resin material which is applied to the glass substrate as the forming die in the third step, so as to cause the high refractive index resin material to extend on the surface thereof;
(Fifth step)
a step for separating the high refractive index resin material which is cured in the fourth step and the first glass substrate from the glass substrate as the forming die, and for applying a low refractive index resin material on the high refractive index resin material which is cured on the first glass substrate; and
(Sixth step)
a step for curing the low refractive index resin material, after piling a second glass substrate on the low refractive index resin material which is applied to the high refractive index resin material in the fifth step so as so cause the low refractive index resin material to extend on the surface thereof.
Also, the method for manufacturing a planar micro-lens, defined in claim 2, comprises the following first through seventh steps:
(First step)
a step for forming a large number of microscopic recess portions forming cylindrical or spherical surfaces on a surface of a glass substrate in a single dimension or two dimensions, by conducting a wet etching through a mask upon the surface of the glass substrate as a forming die;
(Second step)
a step for aligning the large number of the microscopic recess portions densely, by again conducting the wet etching upon the surface of the glass substrate as the forming die on which the microscopic recess portions are formed in the first step, but not through the mask;
(Third step)
a step for transferring a surface configuration of the glass substrate as the forming die, upon which the large number of the microscopic recess portions are formed densely in the second step, onto a reverse forming die made of nickel and so on;
(Fourth step)
a step for applying a separating agent upon the surface of the reverse forming die being formed in the third step, and further for applying thereon a light-curable or heat-curable resin material of low refractive index;
(Fifth step)
a step for curing the low refractive index resin material, after piling a second glass substrate upon the low refractive index resin material which is applied to in the fourth step so as to cause the low refractive index resin material so extend on the surface thereof;
(Sixth step)
a step for separating the low refractive index resin material which is cured in the fifth step and the second glass substrate from the reverse forming die, and for applying a high refractive index resin material on the low refractive index resin material which is cured on the second glass substrate; and
(Seventh step)
a step for curing the high refractive index resin material, after piling a first glass substrate on the high refractive index resin material which is applied to the low refractive index resin material in the sixth step so at to cause the high refractive index resin material to extend on the surface thereof.
Further, the method for manufacturing a planar micro-lens, defined in claim 3, comprises the following first through eighth steps:
(First step)
a step for forming a large number of microscopic recess portions forming cylindrical or spherical surfaces on a surface of a glass substrate in a single dimension or two dimensions, by conducting a wet etching through a mask upon the surface of the glass substrate as a forming die;
(Second step)
a step for aligning the microscopic recess portions densely, by again conducting the wet etching upon the surface of the glass substrate as the forming die on which the large number of the microscopic recess portions are formed in the first step, but not through the mask;
(Third step)
a step for transferring a surface configuration of the glass substrate as the forming die, upon which the large number of the microscopic recess portions are formed densely in the second step, onto a first reverse forming die made of nickel and so on;
(Fourth step)
a step for transferring a surface configuration of the first reverse forming die, which is produced in the third step, onto a second reverse forming die made of nickel and so on;
(Fifth step)
a step for applying a separating agent upon the surface of the second reverse die being formed in the fourth step, and further for applying thereon a light-curable or heat-curable resin material of high refractive index;
(Sixth step)
a step for curing the high refractive index resin material, after piling a first glass substrate upon the high refractive index resin material which is applied to in the fifth step so as to cause the high refractive index resin material to extend on the surface thereof;
(Seventh step)
a step for separating the high refractive index resin material which is cured in the sixth step and the first glass substrate from the second reverse forming die, and for applying a low refractive index resin material on the high refractive index resin material which is cured on the first glass substrate; and
(Eighth step)
a step for curing the low refractive index resin material, after piling a second glass substrate on the low refractive index resin material which is applied to the high refractive index resin material in the seventh step so at to cause the low refractive index resin material to extend on the surface thereof.
For achieving the second object of the present invention, as defined in the present claims 4 through 12, provided is a planar micro-lens having a high refractive index resin material and a low refractive index resin material, being laminated in layers within a region defined between two (2) pieces of glass substrates, wherein microscopic cylindrical surfaces or microscopic spherical surfaces are aligned on a boundary surface of the two kinds of resin material in a single dimension or two dimensions, and said high refractive index resin material is comprised of a resin having thiol bonding (Rxe2x80x94Sxe2x80x94H) or a resin having sulfide bonding (Rxe2x80x94Sxe2x80x94Rxe2x80x2), or a resin being expressed by a general equation, (Rxe2x80x2xe2x80x94Sxe2x80x94Rxe2x80x94Sxe2x80x94Rxe2x80x94Sxe2x80x94Rxe2x80x2), as a main ingredient,
where S is sulfur, H hydrogen, R any one of cyclic unsaturated hydrocarbon, cyclic saturated hydrocarbon, straight chain-like unsaturated hydrocarbon and straight chain-like saturated hydrocarbon, and Rxe2x80x2 any one of organic compounds having acryloyl group, methacryloyl group, epoxy group, isocyanate group, amino group, acyl group, carboxyl group, alkoxylil group, vinyl group.
The main ingredient which forms said high refractive index resin material is properly a polymer, obtained from monomers indicated by the following structural formulae as starting materials thereof; 
(X indicates hydrogen or methyl group, and n an integer from 0 to 2) 
where in the formula, R1 indicates 
CH2xe2x95x90CHCOOCH2CH2xe2x80x94 or CH2xe2x95x90C(CH3)COOCH2CH2xe2x80x94 and Yxe2x80x94R2xe2x80x94Sxe2x80x94R2xe2x80x94 or xe2x80x94R2xe2x80x94Sxe2x80x94(R2Z)xe2x80x94mR2xe2x80x94Sxe2x80x94R2xe2x80x94 (however, R2 indicates alkylene group, while Z oxygen atom or sulfur atom. Also, m indicates an integer from 0 to 3) 
(in the formula, R indicates xe2x80x94CH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, or xe2x80x94CH(CH3)CH2xe2x80x94) 
Also, the low refractive index resin material which is laminated with the high refractive index resin material is properly any one of resins of fluorine group, resins of acryl group, and resins of epoxy group.
Also, any one of boundary surfaces between said glass substrate and the high refractive index resin material, between the glass substrate and the low refractive index resin material, and between the high refractive index resin material and the low refractive index resin material, is coupled through a coupling agent, thereby increasing the bonding power therebetween, as well as effectively preventing any change in color (i.e.: yellow coloring) due to invasion of oxygen into the boundary surfaces. Further, the coupling agent can be comprised of xcex3-glycidepropyl-trimethoxysilane or xcex3-mercaptpropyl-trimethoxysilane.
Also, it is possible to make the high refractive index resin material contain a curing agent of the thiol group. If it contains the curing agent of the thiol group, because an oxide in the main agent is reduced by the thiol, because an impurity which ought to be oxidized and colored is reduced due to the existence of the thiol, and further because it cannot take on a coloring resonant structure due to addition of the thiol, it is possible to prevent coloration of the high refractive index resin material. The curing agent of the thiol group may comprise, for example, pentaerithritol-tetrakisthiopropionate indicated by the following equation (formula 10), or trihydroxyethyl-isocyanate xcex2 mercaptpropionic acid, as indicated by the following equation (formula 11):
Formula 10
(HSCH2CH2COOCH2)4C

Further, it is possible to make the high refractive index resin material contain a curing promotion agent other than the curing agent of the thiol group. The curing promotion agent may comprise, for example, dibutyltin-dilaurate, as indicated by the following formula 12:
Formula 12
[CH2(CH2)3]2Sn[OOC(CH2)10CH3]2
Also, as the glass substrate used in constructing the planar micro-lens, though its type is not particularly restricted, employed may be one made from a quartz glass, a low expansive crystal glass, or a borosilicate glass.
As the low expansive crystal glass can be used xe2x80x9cNeoceram ((copyright))xe2x80x9d by Nippon Denki Glass Co., Ltd., (66SiO222Al2O34LiO22ZrO22TiO2) or xe2x80x9cVycorxe2x80x9d by Corning Inc., (96SiO23B2O31Al2O3).
Further, as examples of the composition of the borosilicate glass, the following are preferable:
(Composition 1)
SiO2: equal to or greater than 45 mass % and equal to or less than 75 mass %;
B2O3: equal to or greater than 8.0 mass % and equal to or less than 19.0 mass %;
BaO: equal to or greater than 4.2 mass % and equal to or less than 14 mass %;
MO (M being a metal of 2-valence other than Ba): equal to or greater than 10 mass % and equal to or less than 30 mass %;
R2O (R being a metal of 1-valence): equal to or less than 10 mass %;
(Composition 2)
SiO2: equal to or greater than 45 mass % and equal to or less than 75 mass %;
B2O3: equal to or greater than 9.5 mass % and equal to or less than 12.5 mass %;
BaO: equal to or greater than 4.2 mass % and equal to or less than 14 mass %;
MO (M being a metal of 2-valence other than Ba): equal to or greater than 10 mass % and equal to or less than 30 mass %;
R2O (R being a metal of 1-valence): equal to or less than 10 mass %;
(Composition 3)
SiO2: equal to or greater than 45 mass % and equal to or less than 75 mass %;
B2O3: equal to or greater than 8.0 mass % and equal to or less than 19.0 mass
BaO: equal to or greater than 4.2 mass % and equal to or less than 14 mass %;
MO (M being a metal of 2-valence other than Ba): equal to or greater than 10 mass % and equal to or lets than 30 mass %;
R2O (R being a metal of 1-valence): equal to or less than 1 mass %;
(Composition 4) 
SiO2: equal to or greater than 45 mass % and equal to or less than 75 mass %;
B2O3: equal to or greater than 8.0 mass % and equal to or less than 19.0 mass %;
BaO: equal to or greater than 4.2 mass % and equal to or less than 10 mass %;
MO (M being a metal of 2-valence other than Ba): equal to or greater than 10 mass % and equal to or less than 30 mass %;
R2O (R being a metal of 1-valence): equal to or less than 10 mass %;